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Manual J Cooling Load (Simplified) - Simplified sensible and latent cooling load estimate.
Manual J Heating Load (Simplified) - Simplified heating load estimate.
Duct Sizing - Round and rectangular duct size from CFM and friction rate.
Static Pressure - Total external static pressure from duct elements.
Refrigerant P-T Chart - Pressure-temperature for common refrigerants.
Superheat and Subcool - Superheat or subcool from line temperature and pressure.
SEER and EER Conversion - Bidirectional rating conversion.
Heat Pump Balance Point - Balance temperature from heating capacity and heat loss.
Sensible Heat Ratio - SHR from total and sensible cooling loads.
CFM per Ton - Standard 400 CFM per ton with humidity adjustments.
Combustion Air - Required combustion air opening from BTU input and room volume.
Max Appliance Input from Room Volume - Largest appliance BTU input a confined space supports by the standard volume method.
Compare Two Refrigerants - Side-by-side P-T at a chosen pressure or temperature with manufacturer attribution.
Refrigerant Charge Weighing - Charge in oz from line-set length, diameter, and refrigerant.
Line-Set Length Refrigerant Charge Adder - The extra refrigerant a longer-than-factory line set needs, added to the nameplate base.
Approach and Delta-T Diagnostics - Condenser approach and supply/return delta-T with band labels.
Outdoor Air Mix - Mixed dry-bulb and humidity ratio from RA/OA states and OA fraction.
Equivalent Length of Fittings - Total equivalent feet from fitting type and diameter counts.
Wet-Bulb Sling Psychrometer - RH, dew point, and GPP from dry-bulb and wet-bulb.
Economic (Least-Cost) Insulation Thickness - The insulation thickness that costs the LEAST over its life, balancing energy saved against insulation bought.
Pipe Insulation Thickness - Required thickness from cylindrical conduction at a target surface temp.
Pipe Insulation for Condensation Control (Cold Lines) - The cold-pipe mirror of insulation-thickness, with the target COMPUTED instead of hand-entered.
Latent Heat Evaporative Cooling - Cooling effect from evaporation rate and h_fg.
Evaporative (Swamp) Cooler Leaving Temperature - The supply-air temperature a direct-evaporative (swamp) cooler delivers.
Indirect Evaporative Cooler Leaving Temperature - The leaving air temperature from an indirect evaporative cooling stage, which cools without adding moisture.
Fan Affinity Laws - What a fan's airflow, static pressure, and power do when you change its speed.
Belt Length and Pulley Speed - V-belt length, driven RPM, and belt speed from pulley diameters and centers.
Compressed Air Receiver Sizing - Required receiver gallons from tool CFM-at-duty-cycle list and pump.
Geothermal Loop Length - Estimated loop length from design BTU and BTU-per-foot benchmarks (simplified).
Hydronic Baseboard Output - BTU/hr from manufacturer-attributed BTU/ft tables interpolated by water temp.
Baseboard Length for a Room Load - The active fin-tube length a room's heat load needs.
Pump NPSH Available - Atmospheric, vapor, static, and friction heads to NPSHa with cavitation flag.
Duct Leakage Test-and-Balance - SMACNA leakage class from measured-vs-design CFM at test pressure; pass/fail against the design class.
Residential Duct Leakage CFM25 (IECC R403.3.5) - Whether a residential duct system passes the energy-code tightness test.
ASHRAE 62.1 Outdoor-Air Ventilation - Breathing-zone and zone outdoor airflow per ASHRAE 62.1 §6.2.2.1.
Commercial Kitchen Hood Exhaust (IMC 507) - Commercial-kitchen hood exhaust airflow for Type I (grease) and Type II (vapor) hoods.
Sensible Heat Ratio / Latent Split (ASHRAE) - Given total cooling Btu/hr, return-air dry / wet-bulb, supply dry-bulb, CFM, and altitude.
Duct Friction Loss and Static Pressure - Darcy-Weisbach with Swamee-Jain Colebrook; round or rectangular; fitting losses from a C_o library.
Refrigerant Superheat / Subcooling (psig-psia toggle) - Saturation T from bundled P-T tables (R-410A / R-32 / R-454B / R-22 / R-134a); per-input psig vs psia toggle.
Cooling Tower Approach and Range - Range, approach, heat rejection (gpm × 500 × range BTU/hr).
Pipe Insulation Heat Loss (bare vs insulated) - Cylindrical conduction + convection + radiation; effectiveness % vs bare.
Chiller Tonnage (Delta-T and GPM) - Cooling capacity (tons, BTU/hr, kW) from chilled-water flow and the entering/leaving temperature split.
Heat Exchanger LMTD and Effectiveness-NTU - Log-mean temperature difference, heat duty, required UA, effectiveness, NTU.
Air Changes per Hour (ACH) - How many times an hour the air in a room is replaced, against the ventilation target for that space.
Boiler Distribution Pipe Sizing - Hydronic GPM = Q / (500 × delta-T), the smallest copper / steel / PEX size at or below the velocity ceiling, velocity.
Compressor Short-Cycle Protection - Estimated cycles per hour from the ASHRAE/AHRI part-load cycling parabola, on/off time.
Humidifier Capacity (RH Target) - Moisture addition (lb/hr, gal/day) and latent load from supply CFM and the entering-to-target RH rise.
Filter Pressure Drop and Fan-Energy Penalty - Clean and change-out pressure drop by MERV / HEPA class (velocity-scaled, user-overridable cut-sheet defaults).
Window Overhang Shading (Profile Angle and Shade Line) - How much of a window a fixed overhang actually shades, as a profile angle and a shade line down the glass.
Window Solar Heat Gain and Conduction Cooling Load - The two ways a window adds to a cooling load.
Internal Heat Gains: People, Lighting, Equipment - The heat the building makes inside: occupant sensible and latent gain from the activity-level rate.
Opaque-Envelope Conduction Cooling Load (Sol-Air CLTD) - The conduction cooling load through a sunlit wall or roof.
Manual D Friction Rate (Available Static Pressure) - The static pressure left over for the duct after the equipment takes its share, and the friction rate that sizes it.
ERV Total Enthalpy Recovery - The total heat an energy-recovery ventilator saves, and the enthalpy of the air it hands the coil.
Radiant Floor Heat Output - How much heat a radiant floor puts out per square foot, and whether the surface stays comfortable.
Hydronic Snowmelt Load and Boiler Sizing (ASHRAE) - The heated-driveway sizing balance: warm the falling snow to the 33 F film.
Economizer Enthalpy Changeover - Differential-enthalpy: enable free cooling when outdoor enthalpy < return (accounts for humidity); fixed-dry-bulb.
Cooling Coil Face Velocity and Carryover Check - Face velocity = CFM / coil face area, checked against the ~500 fpm wet-coil carryover limit.
Cooling Coil Face Area for a Target Velocity - Required coil face area = CFM / target face velocity, the inverse of the face-velocity check.
VAV Box Minimum and Maximum Airflow - The most and the least air a VAV box may deliver to a zone.
Duct Velocity Pressure - Air velocity from velocity pressure or the inverse via V = 4005 x sqrt(VP) for standard air.
Duct Static Regain at a Velocity Decrease - The static pressure a duct RECOVERS when the air slows at a size increase.
Refrigerant Line Velocity and Oil Return - Line velocity from mass flow, inside diameter, and specific volume.
Refrigerant Line Size for Oil Return - The largest refrigerant line inside diameter that still meets the oil-return minimum velocity.
Air-Side Economizer Free-Cooling Hours - Free-cooling capacity and the annual ton-hours an air-side economizer offsets.
Insulated Pipe Heat Loss (Radial) - Radial (cylindrical) conduction heat loss per linear foot and total through pipe insulation via the log-mean form.
Pipe Insulation Thickness for a Target Heat Loss - The pipe insulation thickness that caps radial heat loss at a target rate per foot.
Fan Brake Horsepower - Air horsepower, brake horsepower, and the next standard NEMA motor size from airflow, total static pressure.
Fan Max Airflow from Motor Power - The most airflow a fan motor can move against a total static pressure.
Excess Air from Flue-Gas O2 - Turn a combustion analyzer's oxygen (or CO2) reading into percent excess air.
Air-Free CO Correction - Correct a combustion analyzer's carbon monoxide to an air-free basis.
Draft-Hood Dilution Ratio - How much room air the draft hood pulled in, from two O2 readings.
Theoretical Chimney Draft - Natural draft from the hot-vs-cold density difference.
Chimney Height for a Target Draft - The stack height needed to produce a target NET draft.
Flue-Gas Combustion Efficiency (Stack Loss) - The third number on the analyzer screen, from the same O2 and stack-temperature readings.
Condensing Appliance Flue Condensate Rate - The condensate a high-efficiency condensing furnace, boiler, or water heater drains.
Natural-Gas Flue-Gas Water Dew Point - The WATER dew point of natural-gas combustion products.
Oil Burner Nozzle Firing Rate (GPH) - The oil burner nozzle firing rate (gallons per hour) to hit a target heat OUTPUT.
Combustion Lambda and Air-Fuel Ratio - The lambda and air-fuel ratio a modern analyzer shows beside excess air, from the same flue oxygen.
Liquid-Line Subcooling to Prevent Flash Gas - How much subcooling a system needs to keep the liquid line from flashing.
Hydronic Buffer Tank Sizing (Anti-Short-Cycle) - Buffer-tank volume to stop a boiler or chiller short-cycling.
Hydronic Outdoor Reset Ratio and Supply Target - The boiler outdoor-reset curve: reset ratio = (design supply - min supply) / (no-heat OA - design OA).
Buffer Tank with Distribution-Loop Credit - Net buffer tank after crediting the water already in the distribution loop.
Hydronic Injection-Mixing Loop Flow - The injection flow that feeds a lower-temperature secondary (radiant or reset) loop from a hotter primary.
Control Valve Authority (Beta) - How much control a modulating valve actually has over its branch flow.
Round-to-Rectangular Duct Equivalent - ASHRAE equal-friction equivalent diameter between round and rectangular duct, with an aspect-ratio flag.
Fixed-Orifice Target Superheat (Charging) - The TARGET superheat a fixed-orifice (piston/cap-tube) air conditioner should be charged to for the conditions.
Flat-Oval Duct Equivalent Round Diameter - The equivalent round diameter of flat-oval duct, the size to enter into a friction chart.
Total External Static Pressure - Total external static pressure from a component list, against the blower rating.
Duct Transition (Reducer) Length from Slope - The length a duct size change needs to hold a target transition slope.
Refrigeration Compression Ratio - Absolute compression ratio from suction and discharge pressures, with a high-ratio flag.
Wall Assembly R-Value - The whole-assembly R-value of a framed wall by the parallel-path method.
Blown Insulation Coverage - The bags of blown insulation an attic needs at a target R.
Heat-Pump Seasonal Heating Energy and Cost vs Gas and Resistance - The number that drives every electrification job.
Dual-Fuel Economic Switchover (Heat Pump vs Gas Balance Point) - The setpoint a dual-fuel (hybrid) thermostat should hand off to gas at.
Heat-Pump Cold-Temperature Capacity and Auxiliary Heat - Whether a heat-pump conversion holds on the design day.
Compressed-Air Leak Load and Annual Cost (Load/Unload Test) - Turns a stopwatch reading into a repair budget.
Compressed-Air Pipe Pressure Drop - The shop-air question the compressed-air bench never answered: how much pressure a run loses.
Compressed-Air Compression Power (Isentropic) and Energy Cost - The horsepower and running cost to make a given airflow, from first principles.
Compressed-Air Discharge-Pressure Setpoint Savings - Prices the cheapest compressed-air conservation measure there is: turning the discharge pressure down.
ERV/HRV Sensible Effectiveness and Recovered Load - What an ERV/HRV core gives back: pre-tempered outdoor air, and the load that saves.
Makeup-Air Unit Tempering Load (Sensible, Latent, Total) - The heater or coil a makeup-air unit needs.
Demand-Controlled Ventilation Rate from a CO2 Setpoint - The outdoor air per person that holds a CO2 setpoint.
Pipe Flow Reynolds Number and Regime - The Reynolds number behind every friction-factor decision.
Hydronic System Flow from Load and Delta-T - The most fundamental hydronic number, which every balancing valve, pump, and pipe size starts from.
Pump Specific Speed and Impeller Type - The index that says which impeller a duty wants.
Pump Suction Specific Speed (Nss) - The suction-side companion to specific speed.
Refrigerant Mass Flow from Capacity and Refrigeration Effect - The mass flow refrigerant-velocity takes as a given, derived.
Refrigeration COP and Carnot Limit - The fundamental cycle efficiency a SEER or EER rating never reads.
Condenser Total Heat of Rejection - The load the condenser or cooling tower must shed, which the refrigeration side never computes.
COP Implied by the Heat of Rejection - The COP implied by a measured or rated heat of rejection and the evaporator capacity.
Walk-In Cooler Heat Load - Box load = transmission (U x area x deltaT) + infiltration + product + internal, times a safety factor.
Product Pull-Down Load - Heat to bring product to storage: above freezing Q = m cp deltaT.
Compressor Theoretical Displacement - The swept-volume pumping ceiling of a reciprocating compressor.
Compressor Volumetric Efficiency (Clearance Re-Expansion) - The clearance (theoretical) volumetric efficiency of a reciprocating compressor.
Product Pull-Down Time - Hours to pull product down from the refrigeration capacity dedicated to product load (hours = Q / capacity).
Evaporator Design TD and Humidity Band - The design split between box temperature and suction, and the humidity it holds in the box.
Whole-Building Heat-Loss Coefficient UA - The whole envelope rolled into one number a degree-day estimate and a balance-point calc both start from.
Annual Heating Energy and Fuel Cost from Degree-Days - The annual heating bill an upgrade is measured against.
Wall Condensation Plane Temperature vs Dew Point - The hidden interface an IR reading of the room-side surface never catches.
Duct Heat Gain/Loss Through Unconditioned Space - Duct heat gain or loss through unconditioned space, and the supply-air temperature change.
Grille/Register Face Velocity and Free-Area Sizing - Face velocity V = CFM/(gross area x free-area ratio), or the required gross size from a target velocity.
ADPI Room Air Diffusion Selection (ASHRAE) - Whether a supply outlet will actually mix the room, by the ASHRAE Air Diffusion Performance Index.
Vibration Isolation Efficiency (ASHRAE) - Whether the isolators under a fan, pump, RTU, or chiller actually cut the vibration.
Isolator Static Deflection for a Target Isolation - Enter the running speed and the isolation efficiency you want, get the static deflection to specify for the mount.
Air Density Correction for Altitude and Temperature (ACFM/SCFM) - How much thinner the air is at altitude and temperature, and the ACFM, SCFM, and fan-static corrections that follow.
Moist Air Enthalpy (ASHRAE Psychrometrics) - Total heat content h = 0.240 t + W (1061 + 0.444 t) Btu per lb dry air.
Dry-Bulb from Enthalpy and Humidity Ratio - Dry-bulb temperature of an air state from its enthalpy and humidity ratio.
Cooling Coil Total Load from Enthalpy Difference - The total heat a cooling coil removes, sensible plus latent.
Coil Bypass Factor and Apparatus Dew Point - How much air slips past a coil untouched, and how much actually contacts it.
Fan Sheave Change for a Target CFM - The drive sheave diameter that hits a target airflow.
Fan Affinity Laws (Speed / Diameter Change) - How far airflow, static pressure, and horsepower move when a fan's speed changes.
Pitot Traverse Airflow (Velocity Pressure to CFM) - Duct airflow from a Pitot traverse reading.
Orifice Permanent (Unrecovered) Pressure Loss (ISO 5167) - The permanent pressure loss across a square-edge orifice plate - the head the pump or fan actually pays.
Gas (Compressible) Differential-Pressure Flow Meter - Compressible-gas flow through an orifice plate, from the differential pressure across it.
Differential-Pressure Flow Meter (Orifice / Venturi) - Liquid flow through an orifice plate, venturi, or flow nozzle, from the differential pressure across it.
Pitot Traverse Airflow from Point Readings (Velocity-Averaged) - The correct way to average a Pitot traverse.
Measured Outside-Air Percent from Mixed-Air Temperatures - How much outside air a unit is actually pulling in, read from three temperatures.
Darcy Friction Factor (Swamee-Jain / Colebrook) - The Darcy friction factor for pipe/duct head loss.
Condensate Drain Trap Depth from Fan Static - The dimension condensate-drain only mentions in prose.
Auxiliary Condensate Drain Pan (IRC M1411.3.1) - The overflow protection behind the primary drain, and it turns on one misread sentence.
Condensate Rate and Drain Size - The gallons per hour a coil sheds from the tonnage, the minimum drain-line size by IMC 307.2.2.
Recovery-Cylinder 80% Fill - The maximum net refrigerant a recovery cylinder may legally hold under the 80% fill rule.
TXV Capacity Correction and Valve Sizing - What a thermostatic expansion valve actually delivers where it is installed, against the load it has to feed.
Evaporator Defrost Heat and Cycle Time - How much heat a defrost takes and how long it runs, from the three terms that make it up.
Control Damper Authority and Leakage - Whether a control damper has enough authority to modulate, and how much a closed one leaks.
Chilled-Water Low Delta-T Screen and Pump Penalty - Whether a chilled-water plant is achieving its design delta-T, and what the excess flow is costing in pumping power.
Refrigerant Leak Rate and the EPA Repair Threshold - The annualized refrigerant leak rate that decides whether a repair clock has started.
Refrigerant Recovery Time and Phase Split - How long a recovery takes, and what recovering liquid first is worth.
Low-Ambient Head Pressure Control and Winter Charge - The lowest head pressure a system can be allowed to run at in cold weather.
HVAC Equipment Circuit (MCA / MOCP) - The minimum circuit ampacity and maximum overcurrent device for a condenser or heat pump per NEC 440.33 / 440.22.
Run Capacitor Microfarad Check - In-circuit capacitance of a motor run capacitor from measured volts and amps.
Vacuum Decay (Blank-Off) Test - The evacuation standing-decay verdict: from the micron level at valve-off, the level after a timed hold.
Nitrogen Pressure Test (Temperature-Corrected) - Separates a real leak from thermal swing in a standing nitrogen pressure test.
Gas-Meter Clocking (Actual Firing Rate) - The actual firing rate of a gas appliance by clocking the meter.
Gas-Meter Clock Target Time - The seconds per dial revolution a gas appliance should take if it is firing on rate.
Furnace Temperature Rise and Derived Airflow - The supply-minus-return temperature rise checked against the rating-plate range (default 40 to 70 F).
Furnace Airflow to Temperature Rise - Pick a blower airflow (a tap or a target CFM) and predict the rise it produces, to set the blower before measuring.
Blower-Door Air-Tightness (ACH50, Natural Infiltration, Code Check) - Turns a blower-door reading into the number every weatherization job turns on.
ASHRAE 62.2 Whole-House Mechanical Ventilation Rate - The residential whole-house ventilation a tight house needs.
Infiltration Heating / Cooling Load (Sensible + Latent) - The load the air the envelope leaks adds to the design day.
Boiler Blowdown Heat Recovery and Efficiency Gain - Blowdown volume is set by chemistry, not by a valve position.
Deaerator Steam Demand and Vent Rate - A deaerator heats feedwater to saturation to drive out oxygen.
Boiler Safety Valve Relieving Capacity - The requirement is simple to state and easy to fail after twenty years of modifications.
Fuel Oil Heating for Atomizing Viscosity - Heavy fuel oil will not atomize unless it is thin enough.

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